<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    body{
        display: flex;
    }
    #myCanvus{
        margin: auto;
        margin-top: 50px;
    }
</style>
<body onload="draw()">
    <canvas id="myCanvus" width="300px" height="200px" style="border:1px dashed black;">
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    </canvas>
    <canvas id="Canvas"></canvas>
</body>
<script>
    //五星红旗
    function draw() {
        var canvas = document.getElementById("myCanvus");
        var context = canvas.getContext("2d");

        context.fillStyle = "red";
        context.fillRect(0, 0, 300, 200);

        context.strokeStyle = "yellow";
        context.fillStyle = "yellow"
        var r;

        context.save();

        context.translate(25, 25);

        r = 30;
        context.beginPath();
        context.moveTo(r, 0);
        context.lineTo(r + Math.cos(Math.PI * 3 / 10) * r, r + Math.sin(Math.PI * 3 / 10) * r);
        context.lineTo(r - Math.cos(Math.PI * 1 / 10) * r, r - Math.sin(Math.PI * 1 / 10) * r);
        context.lineTo(r + Math.cos(Math.PI * 1 / 10) * r, r - Math.sin(Math.PI * 1 / 10) * r);
        context.lineTo(r - Math.cos(Math.PI * 3 / 10) * r, r + Math.sin(Math.PI * 3 / 10) * r);
        context.lineTo(r, 0);
        context.fill();
        context.stroke();
        context.closePath();

        context.restore();

        context.save();
        context.translate(100, 10);
        r = 10;
        context.beginPath();
        context.moveTo(r, 0);
        context.lineTo(r + Math.cos(Math.PI * 3 / 10) * r, r + Math.sin(Math.PI * 3 / 10) * r);
        context.lineTo(r - Math.cos(Math.PI * 1 / 10) * r, r - Math.sin(Math.PI * 1 / 10) * r);
        context.lineTo(r + Math.cos(Math.PI * 1 / 10) * r, r - Math.sin(Math.PI * 1 / 10) * r);
        context.lineTo(r - Math.cos(Math.PI * 3 / 10) * r, r + Math.sin(Math.PI * 3 / 10) * r);
        context.lineTo(r, 0);
        context.fill();
        context.stroke();
        context.closePath();

        context.restore();

        context.save();
        context.translate(120, 30);
        r = 10;
        context.beginPath();
        context.moveTo(r, 0);
        context.lineTo(r + Math.cos(Math.PI * 3 / 10) * r, r + Math.sin(Math.PI * 3 / 10) * r);
        context.lineTo(r - Math.cos(Math.PI * 1 / 10) * r, r - Math.sin(Math.PI * 1 / 10) * r);
        context.lineTo(r + Math.cos(Math.PI * 1 / 10) * r, r - Math.sin(Math.PI * 1 / 10) * r);
        context.lineTo(r - Math.cos(Math.PI * 3 / 10) * r, r + Math.sin(Math.PI * 3 / 10) * r);
        context.lineTo(r, 0);
        context.fill();
        context.stroke();
        context.closePath();

        context.restore();

        context.save();
        context.translate(120, 60);
        r = 10;
        context.beginPath();
        context.moveTo(r, 0);
        context.lineTo(r + Math.cos(Math.PI * 3 / 10) * r, r + Math.sin(Math.PI * 3 / 10) * r);
        context.lineTo(r - Math.cos(Math.PI * 1 / 10) * r, r - Math.sin(Math.PI * 1 / 10) * r);
        context.lineTo(r + Math.cos(Math.PI * 1 / 10) * r, r - Math.sin(Math.PI * 1 / 10) * r);
        context.lineTo(r - Math.cos(Math.PI * 3 / 10) * r, r + Math.sin(Math.PI * 3 / 10) * r);
        context.lineTo(r, 0);
        context.fill();
        context.stroke();
        context.closePath();

        context.restore();

        context.save();
        context.translate(100, 80);
        r = 10;
        context.beginPath();
        context.moveTo(r, 0);
        context.lineTo(r + Math.cos(Math.PI * 3 / 10) * r, r + Math.sin(Math.PI * 3 / 10) * r);
        context.lineTo(r - Math.cos(Math.PI * 1 / 10) * r, r - Math.sin(Math.PI * 1 / 10) * r);
        context.lineTo(r + Math.cos(Math.PI * 1 / 10) * r, r - Math.sin(Math.PI * 1 / 10) * r);
        context.lineTo(r - Math.cos(Math.PI * 3 / 10) * r, r + Math.sin(Math.PI * 3 / 10) * r);
        context.lineTo(r, 0);
        context.fill();
        context.stroke();
        context.closePath();
    }

    function getRad(degree) {
        return degree / 180 * Math.PI;
    }
</script>

</html>